1. Field of the Invention
Embodiments of the invention relate to an organic light emitting display.
2. Description of the Related Art
An organic light emitting device adopted in an organic light emitting display is a self light emitting device which has a light emission layer formed between two electrodes. As for the organic light emitting device, electrons and holes are injected into a light emission layer from an electron injection electrode (cathode) and a hole injection electrode (anode), and excitons generated by coupling the injected electrons and holes to each other emit light while falling from an exciton state to the ground state.
Organic light emitting displays using an organic light emitting device are classified into a top emission type, a bottom emission type, a dual emission type, and the like, according to the emitting direction of light, and also are classified into a passive matrix type, an active matrix type, and the like, according to the driving manner.
In these organic light emitting displays, when a scan signal, a data signal, and power are supplied to a plurality of subpixels arranged in a matrix type, the selected subpixels emit light to thus display images.
As for the organic light emitting display, since the threshold voltage of the driving transistor included in the subpixel is shifted, the driving current is lowered over time, and thus the lifespan of the device is decreased. Therefore, the organic light emitting display adopts a compensation circuit for performing compensation of the threshold voltage shift characteristics of the driving transistor. However, in the instance where the compensation circuit is added into the subpixel of the organic light emitting display of a related art, the circuit needs to be implemented within a limited area, and thus the layout efficiency may deteriorate at the time of realizing high resolution. Due to this reason, these difficulties and disadvantages are required to be solved.